# coding=utf-8
from math import sqrt
x1, y1, x2, y2 = map(float, raw_input().split())
print sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2) from math import sqrt x1, y1, x2, y2 = map(float, raw_input().split()) x1 map(float, raw_input().split()) map float raw_input().split() ().split () raw_input split y1 x2 y2 print sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2) sqrt (x1 - x2) ** 2 + (y1 - y2) ** 2 (x1 - x2) ** 2 x1 - x2 x1 x2 2 (y1 - y2) ** 2 y1 - y2 y1 y2 2 x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) x2 y1, x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) y1 y2 = map(float, raw_input().split()) map(float, raw_input().split()) y2 x1, y1, x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) x1
# coding=utf-8
from math import sqrt
x1, y1, x2, y2 = map(float, raw_input().split())
print sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)